Kinetic modelling of anaerobic hydrolysis of solid wastes, including disintegration processes Santiago García-Gen a , Philippe Sousbie c , Ganesh Rangaraj c , Juan M. Lema a , Jorge Rodríguez a,b,⇑ , Jean-Philippe Steyer c , Michel Torrijos c a Department of Chemical Engineering, Institute of Technology, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain b Institute Centre for Water and Environment (iWater), Masdar Institute of Science and Technology, PO Box 54224 Abu Dhabi, United Arab Emirates c INRA, UR50, Laboratoire de Biotechnologie de l’Environnement, Avenue des Etangs, Narbonne F-11100, France article info Article history: Received 14 April 2014 Accepted 10 October 2014 Available online 4 November 2014 Keywords: Anaerobic co-digestion Solid wastes Kinetics Modelling Fractionation ADM1 abstract A methodology to estimate disintegration and hydrolysis kinetic parameters of solid wastes and validate an ADM1-based anaerobic co-digestion model is presented. Kinetic parameters of the model were cali- brated from batch reactor experiments treating individually fruit and vegetable wastes (among other res- idues) following a new protocol for batch tests. In addition, decoupled disintegration kinetics for readily and slowly biodegradable fractions of solid wastes was considered. Calibrated parameters from batch assays of individual substrates were used to validate the model for a semi-continuous co-digestion oper- ation treating simultaneously 5 fruit and vegetable wastes. The semi-continuous experiment was carried out in a lab-scale CSTR reactor for 15 weeks at organic loading rate ranging between 2.0 and 4.7 g VS/L d. The model (built in Matlab/Simulink) fit to a large extent the experimental results in both batch and semi-continuous mode and served as a powerful tool to simulate the digestion or co-digestion of solid wastes. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction The high production and disposal of organic solid wastes and their uncontrolled decomposition generates a large-scale environ- mental pollution. Particularly, fruit and vegetable wastes (FVW) that are highly biodegradable constitute a source of methane emis- sion, odours and air contamination in municipal landfills (Garcia- Peña et al., 2011). In order to reduce and stabilise the volume of organic wastes, anaerobic digestion has become an alternative technology against incineration or composting and has been proved as a well establish process for the treatment of many types of organic wastes, solids or liquids (Bouallagui et al., 2009). Among biological treatments, anaerobic digestion or co-digestion is the most cost-effective, due to the high energy recovery as biogas and its limited environmental impact (Mata-Alvarez et al., 2000), and can be applied to FVW in order to raise the value of this kind of wastes. Anaerobic Digestion (AD) consists on the biological degradation of organic matter by the action of a microbial consortium that con- verts organic substrates into methane and carbon dioxide through a complex reaction path. The mechanism involves a series of paral- lel and sequential stages: hydrolysis, acidogenesis, acetogenesis/ dehydrogenation, and methanation, each one catalysed by a partic- ular group of microorganisms (Gupta et al., 2012). Recently, the interest is growing on anaerobic co-digestion (AcoD). The term co-digestion stands for the simultaneous diges- tion of two or more organic substrates, and has become more attractive than single-substrate AD due to several advantages such as the improvement of the balance of nutrients and ratio C/N, dilu- tion of toxics and inhibitors or achievement of higher biogas yield and methane production (Khalid et al., 2011; Mata-Alvarez et al., 2011). The co-digestion benefits from the synergism of the differ- ent characteristics of the co-substrates (Hartmann et al., 2003). In 2002, the IWA task group for mathematical modelling devel- oped the Anaerobic Digestion Model No. 1, ADM1 (Batstone et al., http://dx.doi.org/10.1016/j.wasman.2014.10.012 0956-053X/Ó 2014 Elsevier Ltd. All rights reserved. Abbreviations: AcoD, anaerobic co-digestion; AD, Anaerobic Digestion; ADM1, Anaerobic Digestion Model No. 1; BMP, biochemical methane potential; C/N, carbon to nitrogen ratio; COD, chemical oxygen demand; CSTR, continuous stirred tank reactor; FVW, fruit and vegetable wastes; HRT, hydraulic retention time; LCFA, long chain fatty acids; OLR, organic loading rate; TS, total solids; VFA, volatile fatty acids; VS, volatile solids; VSS, volatile suspended solids. ⇑ Corresponding author at: Institute Centre for Water and Environment (iWater), Masdar Institute of Science and Technology, PO Box 54224 Abu Dhabi, United Arab Emirates. Tel.: +971 2 810 9173. E-mail address: jrodriguez@masdar.ac.ae (J. Rodríguez). Waste Management 35 (2015) 96–104 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman